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參數(shù)資料
| 型號： | LM25005MHX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 42V, 2.5A STEP-DOWN SWITCHING REGULATOR |
| 中文描述： | 4.25 A SWITCHING REGULATOR, 525 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | TSSOP-20 |
| 文件頁數(shù)： | 11/21頁 |
| 文件大?。?/td> | 756K |
| 代理商： | LM25005MHX |
Shutdown / Standby
The LM25005 contains a dual level Shutdown (SD) circuit.
When the SD pin voltage is below 0.7V, the regulator is in a
low current shutdown mode. When the SD pin voltage is
greater than 0.7V but less than 1.225V, the regulator is in
standby mode. In standby mode the Vcc regulator is active
but the output switch is disabled. When the SD pin voltage
exceeds 1.225V, the output switch is enabled and normal
operation begins. An internal 5μA pull-up current source
configures the regulator to be fully operational if the SD pin is
left open.
An external set-point voltage divider from Vin to GND can be
used to set the operational input range of the regulator. The
divider must be designed such that the voltage at the SD pin
will be greater than 1.225V when Vin is in the desired
operating range. The internal 5μA pull-up current source
must be included in calculations of the external set-point
divider. Hysteresis of 0.1V is included for both the shutdown
and standby thresholds. The voltage at the SD pin should
never exceed 8V. When using an external set-point divider, it
may be necessary to clamp the SD pin to limit its voltage at
high input voltage conditions.
The SD pin can also be used to implement various remote
enable / disable functions. Pulling the UVLO pin below the
0.7V threshold totally disables the controller. If the SD pin
voltage is above 1.225V the regulator will be operational.
Oscillator and Sync Capability
The LM25005 oscillator frequency is set by a single external
resistor connected between the RT pin and the AGND pin.
The R
resistor should be located very close to the device
and connected directly to the pins of the IC (RT and
AGND).To set a desired oscillator frequency (F), the neces-
sary value for the R
T
resistor can be calculated from the
following equation:
The SYNC pin can be used to synchronize the internal
oscillator to an external clock. The external clock must be of
higher frequency
than the free-running frequency set by
the R
T
resistor.Aclock circuit with an open drain output is the
recommended interface from the external clock to the SYNC
pin. The clock pulse duration should be greater than 15 ns.
Multiple LM25005 and/or LM5005 devices can be synchro-
nized together simply by connecting the SYNC pins together.
In this configuration all of the devices will be synchronized to
the highest frequency device. The diagram in Figure 5 illus-
trates the SYNC input/output features of the LM25005. The
internal oscillator circuit drives the SYNC pin with a strong
pull-down / weak pull-up inverter. When the SYNC pin is
pulled low either by the internal oscillator or an external
clock, the ramp cycle of the oscillator is terminated and a
new oscillator cycle begins. Thus, if the SYNC pins of sev-
eral LM25005 IC’s are connected together, the IC with the
highest internal clock frequency will pull the connected
SYNC pins low first and terminate the oscillator ramp cycles
of the other IC’s. The LM25005 or LM5005 with the highest
programmed clock frequency will serve as the master and
control the switching frequency of the all the devices with
lower oscillator frequency.
20170005
FIGURE 3. Sync from External Clock
20170006
FIGURE 4. Sync from Multiple Devices
L
www.national.com
11
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM25005MHX/NOPB | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM25007 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Boot Capacitor Regulation in LM25007 Constant-On-Time (COT) Converter |
| LM25007_08 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:42V, 0.5A Step-Down Switching Regulator |
| LM25007_11 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Boot Capacitor Regulation in LM25007 Constant-On-Time (COT) Converter |
| LM25007EVAL | 功能描述:電源管理IC開發(fā)工具 LM25007 EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
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